How to share a run or a ride without giving away where you live

Cut the file, not just the map. A sharing site's privacy zone hides the start and end of a track from other people on that site; the GPX you export, or that a friend downloads, or that another app pulls through the site's link, is the whole track with the time on every point. TRAIL opens a GPX or TCX in the browser, draws it with no map under it, cuts a distance from each end and everything inside a circle round any place you mark, drops the times and the body data, and writes a plain GPX that is safe wherever it goes. Nothing is uploaded, and no map tiles are fetched round your house.

What a track gives away

• Where you live. The first and last points are your door, or within a few metres of it. The track does not have to be public for long; it has to be seen once.
• When you are out. Every point has a timestamp. Across a month of tracks that is the hours the house is empty, on which days, and how long for.
• Where else you go. The gym, the office, a friend's house, the school, all of them a turn-around point or a pause in the track.
• Your body. A TCX or a GPX with extensions carries heart rate, cadence and power, which is health data, and the name of the device that recorded it.
• The pattern. One track is a route. Fifty tracks from the same door, shared under the same name, are a map of a life. This is the one people forget: the cut has to survive comparison across everything you have shared, not just protect one file.

Why a privacy zone is not enough

The large sharing sites let you draw a circle round your home and hide the part of every track inside it from other users. It is worth doing, and it is not the same as removing it. The site still holds the whole track, and the whole track is what leaves when you export the activity, when a training app connected to your account pulls it, when a group ride is shared, and when somebody downloads a route you published. The hiding is a view setting on one website. The address is in the file.

Some sites now also trim a fixed distance from the start and end on the map. The same limits apply: the map is cropped, the file is not, and a short out-and-back from your door leaves a track whose remaining half points straight at it.

How much to cut

More than the distance to the corner. A cut of two hundred metres hides your door and shows your street. Five hundred metres hides which street. A kilometre hides the neighbourhood. If you run the same loop from the same door, the cut has to be wide enough that fifty trimmed tracks do not all begin on one small circle, because they will be looked at together. TRAIL cuts a distance you set from each end, and separately cuts everything inside a circle round any point you mark, so the office and the school go the same way as the house.

Direction still says something. A trimmed track that begins a kilometre from home and heads away from it points back along its first few hundred metres. If that matters to you, cut wider, or start recording once you are away from the house, which is the only method that keeps the address out of the original.

The times and the body data

The timestamps are the part most trimming tools leave in, and they are the part that turns a route into a schedule. Dropping them is on by default in TRAIL; the track keeps its shape and its distance and loses its clock. Heart rate, cadence, power and the device name are dropped with them unless you keep them on purpose. Elevation stays, because it is what makes a ride worth looking at, and it says nothing about where the track started.

Why there is no map

Drawing the track over a map means asking a tile server for the map squares around the track, which is to say around your house, at the moment you are trying to remove your house from a file. TRAIL draws the line on a blank canvas. It is enough to see where the cuts land, and it asks nobody for anything.

What this does not do

It does not go back and fix tracks you have already shared; those are out. It does not change the original file on your device, only write a new one. It does not hide you from the sharing site itself, which has the original from the watch or the phone unless you trim before uploading. And it does not make a route unrecognisable to somebody who knows the area: a distinctive loop is still a distinctive loop, cut or not. It removes the address, the clock and the body from the file. The rest is judgement about what to share at all.